pidns: Don't allow new processes in a dead pid namespace.
Set nr_hashed to -1 just before we schedule the work to cleanup proc.
Test nr_hashed just before we hash a new pid and if nr_hashed is < 0
fail.
This guaranteees that processes never enter a pid namespaces after we
have cleaned up the state to support processes in a pid namespace.
Currently sending SIGKILL to all of the process in a pid namespace as
init exists gives us this guarantee but we need something a little
stronger to support unsharing and joining a pid namespace.
Acked-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/kernel/pid.c b/kernel/pid.c
index e957f8b..9c21911 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -274,8 +274,10 @@
for (i = 0; i <= pid->level; i++) {
struct upid *upid = pid->numbers + i;
hlist_del_rcu(&upid->pid_chain);
- if (--upid->ns->nr_hashed == 0)
+ if (--upid->ns->nr_hashed == 0) {
+ upid->ns->nr_hashed = -1;
schedule_work(&upid->ns->proc_work);
+ }
}
spin_unlock_irqrestore(&pidmap_lock, flags);
@@ -321,6 +323,8 @@
upid = pid->numbers + ns->level;
spin_lock_irq(&pidmap_lock);
+ if (ns->nr_hashed < 0)
+ goto out_unlock;
for ( ; upid >= pid->numbers; --upid) {
hlist_add_head_rcu(&upid->pid_chain,
&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
@@ -331,6 +335,8 @@
out:
return pid;
+out_unlock:
+ spin_unlock(&pidmap_lock);
out_free:
while (++i <= ns->level)
free_pidmap(pid->numbers + i);
